This invention relates to a solar cell module, and in particular to a thin film solar cell module which is useful for a power generation from sunlight.
There is known the following method as one of the methods for manufacturing a thin film solar cell module. Namely, a transparent electrode layer, a photoelectric semiconductor layer and a metal layer, which have been deposited on a light-transmitting glass substrate, are at least partially worked by means of an optical beam thereby to partition these layers into a plurality of cells to isolate one cell from another cell, which are then electrically connected with each other, and after terminals are attached to these cells, the reverse surface (the surface opposite to the light-transmitting glass substrate) is sealed with an encapsulant such as a resin for protecting the power-generating portions thereof, the resultant body being finally fixed to a mounting frame.
The dielectric strength is one of the characteristics demanded for a solar cell module manufactured in this manner. The dielectric strength of solar cell module can be determined generally by measuring the withstand voltage between a terminal of solar cell and the frame.
The thin film solar cell is generally constituted by a lamination of thin films such as a transparent electrode layer, a photoelectric semiconductor layer and a metal layer, and most of these layers are generally formed through a vapor phase reaction. Accordingly, it is generally difficult, in the process of forming such a laminate through this vapor phase reaction, to restrict film forming area to so-called active portion of the solar cell. Occasionally, any of these layers may extend also to the other surface of the substrate. If such a substrate is attached as it is to the frame, it is more likely that the electric potential of the frame may become identical with that of the active portion of the solar cell. Because of this, the conventional thin film solar cells are generally poor in dielectric strength.
With a view to overcome this problem, there has been proposed a method wherein the active region occupying the central portion of solar cell is electrically isolated from the peripheral region of solar cell, which has much possibilities of being electrically contacted with the frame, by making use of a laser beam which is employed in the patterning of the layers at the occasion of electrical connection of cells. However, the solar cell module manufactured by making use of this method is accompanied with a problem that even though the solar cell exhibits an excellent dielectric strength immediately after the manufacture thereof, this property of dielectric strength is sharply deteriorated when the solar cell module is left in an environment of high temperature and high humidity. Accordingly, this method has been found poor not only in manufacturing yield due to a low reliability but also in productivity, thus making this method useless in industrial viewpoint.
The thin film solar cell module of this kind is especially accompanied with a problem that when it is employed out of door, water may be penetrated into the active portion (power generating region) of the solar cell, thus denaturing or corroding this active portion, resulting in a deterioration of the power-generating property thereof. One of the causes of this problem is the penetration of water through an interface between the substrate and the encapsulant at the peripheral portion of the solar cell module. Therefore, it is highly desired to prevent the penetration of water through a peripheral portion of the solar cell module and to improve the weather resistance of the solar cell module.